Creating a Temper Line or Hamon using the Jim Crowell Method
This is an explanation of how I create a simple Japanese style Hamon or temper line. It has occurred to me over the years that it is far better to only austenize the part you want tempered than to austenize the whole blade and then attempt to localize the â€œhardeningâ€. It was apparent in several test specimens of the latter that hardening occurred far above the immersion line and was not reliable.
I have used 1084, O-1, 1095, L-6 and 5160 all with varying degrees of success. I am still learning about this myself and do not profess to be an â€œexpertâ€. However, heat treat is one of the quixotic intangibles that are hard to prove. If a guy says to me â€œI can cut ten 1inch ropesâ€, I can say, â€œShow me.â€ Unfortunately it is not so simple with heat treat. I will want to know about some exotic heat treat when it has been demonstrated to me unequivocally that it is producing a superior blade; otherwise I really do not want to hear about it.
This process, to me, is simple to understand and hard to accomplish. (It is like going on a diet and exercising; easy to understand but hard to do.)
This process requires some skill with a torch and recognizing the thermal/ color relationship in the steel. Not only must you know what â€œcriticalâ€ looks like but also know when you can quench as the temperature and color drop. It is very easy to overheat the blades and I have ruined many. I am confident with this method as done by myself and have made many test blades at Hammer-ins and the ABS School that were used with excellent results. I have also heat-treated competition knives in this fashion and have never had one fail.
I select a torch tip that appears to be adequate for the size of the blade. I grip the blade by the tang with vise grips, making sure it will not move while being moved rapidly. The quenchant is warm and near at hand. I dim the lights in the shop and set the torch to a medium flame for the chosen tip. If you have too small a tip it will take forever and will probably harden spottily. If the tip is too big it will â€œwash outâ€ the wavy line/s you are attempting. The idea is to have an undulating, cloudy line that wraps the point in some fashion. I very much prefer to harden 1/3 to Â½ of the blade. I do not anneal and therefore the spine of my blade has a bit more resilience than an annealed blade. If you anneal it is all the more important to harden farther up the blade particularly with blades that are thinner.
Holding the blade with the vise grips I pre-heat the ricasso area as well as the spine near the point. These are the areas with the most mass and will suck the heat out the fastest. Also it is unacceptable to have the temper line â€œrun outâ€ prior to traversing the entire cutting edge. I have seen many examples where the last inch or so near the ricasso is was not properly heat-treated. (Hardened)
Now I slowly and evenly maintain the heat in the ricasso and point spine while â€œfilling in: between them. So far so good; from here it is a cinch to have a nice straight line. But to make the waves; When the blade is near â€œcriticalâ€ heat I start to undulate the torch going from one side of the blade to the other as evenly as I can. They never seem to come out evenly although I try to make the waves the same on both sides. The trick is to have everything the right temperature at once, which is hard for me and then get it in the quench tank in that instant. Let it cool a little after quenching and then grind it to see what you got. If you like it go on and finish the knife. If you do not like itâ€¦then do it again. So long as you did not overheat it you can do it again. Very important to have the ricasso area up to heat as this is a real stress riser area. (Now how do I know that?) Draw the temper in whatever manner you like. I treat blades hardened like this the same as my other blades: I draw the overall temper, tang and spine just like my other blades.
Sometimes I dunk it in Ferric Chloride to get a peek. Then, I finish grind and polish by hand to 600 grit. At this point I immerse the blade in PCB etchant (Ferric Chloride, not that other stuff.) Sometimes I rub it out with the 1000 grit automotive wet dry paper and then use the back of the paper. Try different papers and grits and see what you think looks good. Be sure to wash the Etchant off the blade first, as this stuff is quite corrosive.
Be careful of the blade now as you canâ€™t just sand it or buff it at this point or you will ruin the etched finish you just spent so much time creating. I have the shoulders finished and the guard ready prior to etching.
The following are some questions, with my answers, that were asked regarding this process
What quenchant do you use? I use Texaco product Quenchtex B at 120 degrees F
Do you cool the whole blade, tang and all? I quench the blade vertically to just past the ricasso and submerge the tang somewhat. In this process the tang is not brought up to critical heat but I am a creature of habit and tend to want to keep the tang out of the oil. (This would keep it from hardening if I were to be â€œfullyâ€ quenching a blade.)
Some of the terms used in heat-treating get used (incorrectly) and interchangeably. For instance:
HEAT TREATMENT - An operation or combination of operations involving the heating and cooling of a metal or an alloy in the solid state for the purpose of obtaining certain desirable conditions or properties.
NORMALIZING - Heating steels to approximately 100 F above the critical temperature range followed by cooling to below that range in still air at ordinary temperatures. This heat treat operation is used to erase previous heat treating results in carbon steels to .40% carbon, low alloy steels, and to produce a uniform grain structure in forged and cold worked steel parts.
ANNEALING - Applies normally to softening by changing the microstructure and is a term used to describe the heating and cooling cycle of metals in the solid state. The term annealing usually implies relatively slow cooling in carbon and alloy steels. The more important purposes for which steel is annealed are as follows: To remove stresses; to induce softness; to alter ductility, toughness, or electric, magnetic or other physical and mechanical properties; to change the crystalline structure; and to produce a definite microstructure.
HARDENING - The heating and quenching of certain iron-base alloys from a temperature above the critical temperature range for the purpose of producing a hardness superior to that obtained when the alloy is not quenched. This term is usually restricted to the formation of martensite.
OIL HARDENING â€“ This is a process of hardening a ferrous alloy of suitable composition (generally alloys) by heating within or above the transformation range and quenching in oil.
QUENCHING AND TEMPERING - In this operation the procedure consists of heating the material to the proper austenitizing temperature, holding at that temperature for a sufficient time to effect the desired change in crystalline structure, and quenching in a suitable medium - water, oil or air depending on the chemical composition. After quenching, the material is reheated to a predetermined temperature below the critical range and then cooled under suitable temperatures (tempering).
Note: The answers to the above heat-treating questions came from:
I strongly suggest one take the initiative and use the Internet or other sources to find information. All of this information is readily available.
Most of the time annealing is required if you are going to stamp your blade and do file work, etc. With etching it doesnâ€™t have to be soft so one need only normalize. (I do it twice.).
Torch tips/ sizes: as stated on page one, paragraph four: Please review that paragraph.
There several types of oxy acetylene torch tips. There is a cutting tip to actually cut through steel and even this can be used if necessary. There is a very large tip called a Rosebud for heating large items. I have found no use for the Rosebud in this process. The rest of the tips are â€œregularâ€ tips and are numbered in size. I use smaller tips on smaller knives and larger tips on larger knives. It is important to use a tip that allows you to get the blade heated in an amount of time you can manage. It is trial and error.